At present, little is known about the psychodynamics underlying experimentation with, or habitual use of, illicit drugs. Yet, the incidence of such experimentation and use by students has reached an alarming level. We must learn more about why some students become drug dependent, while others experiment only occasionally, and still others never experiment at all. By studying drug-taking behavior in association with personality, attitudes toward drug-taking, and academic performance, we expect to obtain information which will help elucidate the psychodynamics which lead to varying patterns of drug-taking behavior. We plan to study relations among six categories of variables: drug- taking, attitudes toward drug-taking, cigarette smoking, attitudes toward cigarette smoking, personality, and academic performance. Cross- sectional analyses will be performed to study each category of variables in relation to each of the other five categories at a given point in time. Longitudinal analyses will be performed to obtain information concerning sequences of change. For cross-sectional analyses the sample will consist of 23,000 students from grades 4 to 12. For longitudinal analyses the samples will range from 5,000 to 12,000 depending on the length of time separating the earlier and later testings. Standard univariate and multivariate statistical procedures will be used to analyze the data.